Coated diaphragm and battery

Abstract

The utility model provides a coating film structure and a battery. A coating diaphragm comprises a base material and a coating layer formed on one side or two sides of the base material, the coating comprises a first coating part and a second coating part; the first coating part is in contact with the base material, and the second coating part is located on the side, away from the base material, of the first coating part; wherein the first coating part and the surface layer of the base material form a first cross-linked structure, and the second coating part is a second cross-linked structure; the first cross-linked structure and the second cross-linked structure are both of a net structure, the first cross-linked structure and the second cross-linked structure are of an integrated cross-linked structure, and the first average pore size of the first cross-linked structure is larger than the second average pore size of the second cross-linked structure. Through the arrangement of the first cross-linked structure and the second cross-linked structure, the base material and the coating are integrated, so that the peeling strength and the electrolyte soaking resistance of the coated diaphragm are greatly enhanced.

Description

Technical Field

[0001] The utility model relates to the field of battery diaphragms, and particularly to a coated film structure and a battery. Background Art

[0002] The separator is one of the core components of lithium batteries. The quality of its performance has a very important impact on the overall performance of lithium batteries and is one of the key technologies restricting the development of lithium batteries. With the continuous expansion of the application fields of lithium batteries and the deepening of the influence of lithium battery products in people's lives, people's requirements for the performance of lithium batteries are getting higher and higher. In order to meet the development requirements of lithium batteries, as an important component of lithium batteries, the separator should not only have good chemical stability and low manufacturing cost, but also improving the safety performance of lithium batteries is an important trend in the current development of lithium batteries.

[0003] In the existing related technologies, the coated separator may include a base film and a coating applied to at least one surface of the base film, and a cross-linked structure may be formed in the coating. However, the peel strength and the degree of resistance to electrolyte immersion of the coated separator in the existing technologies are still insufficient.

[0004] Therefore, it is necessary to improve the existing coated separator. Summary of the Utility Model

[0005] The technical problem solved by the utility model is to provide a coated film structure and a battery to enhance the peel strength and the degree of resistance to electrolyte immersion of the coated separator.

[0006] According to a first aspect of the utility model, there is provided a coated separator, comprising: a base material and a coating formed on one or both sides of the base material; the coating includes a first coating portion and a second coating portion; the first coating portion is in contact with the base material, and the second coating portion is located on a side of the first coating portion away from the base material; wherein, a first cross-linked structure is formed between the first coating portion and the surface layer of the base material, and the second coating portion is a second cross-linked structure;

[0007] Both the first cross-linked structure and the second cross-linked structure are network structures, and the first cross-linked structure and the second cross-linked structure are an integrated cross-linked structure, and a first average pore size of the first cross-linked structure is larger than a second average pore size of the second cross-linked structure.

[0008] In some embodiments, the first average pore size is: 40 - 46 nm, and the second average pore size is: 39 - 45 nm.

[0009] In some embodiments, the degree of cross-linking of the second cross-linked structure is greater than the degree of cross-linking of the first cross-linked structure.

[0010] In some embodiments, the gel fraction of the second crosslinked structure is 67%-85%, and the gel fraction of the first crosslinked structure is 20%-35%.

[0011] In some embodiments, the thickness of the first crosslinked structure is 0.01-6 μm, and the thickness of the second crosslinked structure is 0.5-5 μm.

[0012] In some embodiments, the material of the substrate is an organic material.

[0013] In some embodiments, the total thickness of the substrate is 5-12 μm.

[0014] In some embodiments, the thickness of the surface layer of the substrate that forms the first crosslinked structure with the first coating portion is 0.01-6 μm.

[0015] Further preferably, the thickness of the surface layer of the substrate that forms the first crosslinked structure with the first coating portion is 0.01-1 μm.

[0016] According to a second aspect of the present invention, there is provided a battery, comprising: a separator, a positive electrode, a negative electrode, and an electrolyte, wherein the separator is the coated separator described in any one of the foregoing items.

[0017] Compared with the prior art, the technical solutions of the embodiments of the present invention have the following beneficial effects:

[0018] For the coated separator provided by the present invention, the first coating portion extends into the surface and holes of the substrate and forms a first crosslinked structure with the surface layer of the substrate. The second coating portion is a second crosslinked structure, and the first crosslinked structure and the second crosslinked structure are an integrated crosslinked structure; through the arrangement of the first crosslinked structure and the second crosslinked structure, the substrate and the coating are integrated, thereby greatly enhancing the peel strength of the coated separator and the degree of resistance to electrolyte immersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of a coated separator provided by an embodiment of the present invention;

[0020] Figure 2 is a schematic structural diagram of a coated separator provided by another embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] As described in the background art, there are problems with the stripping strength and the degree of resistance to electrolyte immersion of the coated separator in the prior art.

[0023] Before filing this application, the applicant conducted sufficient research and experiments on the coated separator in the prior art and found that the reasons for the insufficient stripping strength and the degree of resistance to electrolyte immersion of the coated separator in the prior art are as follows:

[0024] The coated separator in the prior art is a lithium battery separator with an interpenetrating network structure obtained by first coating PVDF on a substrate, drying it, then coating acrylate, and drying it again. The coatings are all organic polymers, and the coatings are independent of the base film, and the polymers in the coatings are also separated from each other. As a result, the coated separator in the prior art has problems with insufficient stripping strength and the degree of resistance to electrolyte immersion.

[0025] In view of this, after the applicant of the present utility model studied and understood the above reasons, the coated separator was improved to obtain the technical solution of the present utility model. The exploration of the above reasons is a prerequisite for the technical solution of this application. Therefore, when considering the novelty of the present utility model, the exploration of the above reasons and the technical solution of the present utility model should be regarded as a whole.

[0026] The technical solution of the present utility model will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0027] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of the coated separator provided by an embodiment of the present utility model; as Figure 1 shown, the coated separator provided by an embodiment of the present utility model includes: a substrate and a coating formed on one side of the substrate; the coating includes a first coating portion and a second coating portion; the first coating portion is in contact with the substrate, and the second coating portion is located on the side of the first coating portion away from the substrate; wherein, the first coating portion and the surface layer of the substrate form a first cross-linked structure 102, and the second coating portion is a second cross-linked structure 201;

[0028] Both the first cross-linked structure 102 and the second cross-linked structure 201 are network structures, and the first cross-linked structure 102 and the second cross-linked structure 201 are an integrated cross-linked structure, and the first average pore size of the first cross-linked structure 102 is greater than the second average pore size of the second cross-linked structure 201.

[0029] Specifically, as Figure 1As shown, the base material therein includes, for example, a first base material portion 101 and a surface layer portion, and a first crosslinked structure 102 is formed between the surface layer portion and the first coating portion. Herein, the surface layer portion generally refers to the portion starting from the surface of the base material and not exceeding 50% of the total thickness of the base material.

[0030] For the coated separator provided by the present utility model, the first coating portion extends into the surface and the interior of the holes of the base material, and a first crosslinked structure 102 is formed with the surface layer of the base material, and a second crosslinked structure 201 is formed with the second coating portion, and the first crosslinked structure 102 and the second crosslinked structure 201 are an integrated crosslinked structure; through the arrangement of the first crosslinked structure 102 and the second crosslinked structure 201, the base material and the coating are integrated into one, thereby greatly enhancing the peel strength and the degree of resistance to electrolyte immersion of the coated separator.

[0031] In some embodiments, the first average pore diameter is: 40 - 46 nm, for example, it can be 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, etc. or the range value between any two numerical values. Of course, it should be realized that the present utility model is not limited thereto, and the first average pore diameter can also be other values as long as it is within 40 - 46 nm.

[0032] The second average pore diameter is: 39 - 45 nm, for example, it can be 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, etc. or the range value between any two numerical values. Of course, it should be realized that the present utility model is not limited thereto, and the second average pore diameter can also be other values as long as it is within 39 - 45 nm.

[0033] In addition, it should be noted that among the foregoing numerical values, the prerequisite that the first average pore diameter is greater than the second average pore diameter needs to be satisfied; for example, when the second average pore diameter is 39 nm, the first average pore diameter can be any value between 40 - 46 nm; when the second average pore diameter is 40 nm, the first average pore diameter is a value greater than 40 nm and less than 46 nm; when the second average pore diameter is other values within the foregoing numerical range, similar treatments are carried out and will not be elaborated here one by one. Setting the first average pore diameter to a value larger than the second average pore diameter is beneficial to the mutual interpenetration and riveting of the crosslinked structure and the surface layer of the base material.

[0034] As an example, the first average pore diameter can be, for example: 43.3 nm, and the second average pore diameter can be, for example: 42 nm.

[0035] Among them, the crosslinking degree of the second crosslinking structure 201 is greater than that of the first crosslinking structure 102. The crosslinking degree can be further characterized by, for example, the gel fraction. As an implementation manner, the gel fraction of the second crosslinking structure 201 is 67%-85%, and the gel fraction of the first crosslinking structure 102 is: 20%-35%. Specifically, by way of example, the gel fraction of the second crosslinking structure 201 can be, for example, 67%, 75%, 80%, 85%, etc. or a range value between any two values; the gel fraction of the first crosslinking structure 102 can be, for example: 20%, 25%, 30%, 35%, etc. or a range value between any two values. Of course, it should be realized that the present utility model is not limited thereto, and the gel fraction of the second crosslinking structure 201 and / or the gel fraction of the first crosslinking structure 102 can also be other values as long as they are within the corresponding numerical ranges.

[0036] It should be noted that both the crosslinking degree and the gel fraction are well-known parameter characterizations in the art, and the crosslinking degree or the gel fraction will affect the pore size of the corresponding structure. Among them, the evaluation method of the crosslinking rate is: peel off the second coating, use a certain weight of toluene M1, extract it at 60°C for 12 hours, and record the total amount of the extracted solvent and polymer as M2, and weigh it after drying as M3. Calculate the gel fraction according to the formula, gel fraction = M3 / (M2 - M1)*100, and the gel fraction is proportional to the crosslinking amount (characterization of the crosslinking degree). The gel fraction of the first crosslinking structure can be obtained in the same way. Thus, the gel fraction of the second coating calculated is 67%-85%, while the gel fraction of the first crosslinking structure is 20%-35%.

[0037] In some embodiments, the thickness of the first crosslinking structure is 0.01-6 μm; as a preferred implementation manner, the thickness of the first crosslinking structure is, for example, 0.02-2 μm; for example, it can be 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm,

[0038] 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc. or a range value between any two values. Of course, it should be realized that the present utility model is not limited thereto, and the thickness of the first crosslinking structure can also be other values as long as it is within 0.01-6 μm. Among them, the thickness of the first crosslinking structure defines the reaction depth of the crosslinking reaction.

[0039] The thickness of the second crosslinked structure is 0.5 - 5 μm; as a preferred embodiment, the thickness of the second crosslinked structure is 0.5 - 3 μm; for example, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. or the range value between any two values. Of course, it should be realized that the present invention is not limited thereto, and the thickness of the second crosslinked structure can also be other values as long as it is within 0.5 - 5 μm.

[0040] In some embodiments, the material of the substrate is an organic material, for example, it can be one or several of a polyolefin microporous membrane, a polyimide microporous membrane, a non-woven fabric separator, a multi-layer composite separator, a ceramic-coated separator, and a polymer-coated separator. Of course, the above materials are all existing materials, and the present invention only selects from the above materials.

[0041] In some embodiments, the total thickness of the substrate is 5 - 12 μm. For example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, etc. or the range value between any two values. Of course, it should be realized that the present invention is not limited thereto, and the thickness of the substrate can also be other values as long as it is within 5 - 12 μm.

[0042] In some embodiments, the thickness of the surface layer of the substrate that forms the first crosslinked structure with the first coating portion is 0.01 - 6 μm, for example, it can be 0.01 μm, 0.05 μm, 0.1 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc. or the range value between any two values. Of course, it should be realized that the present invention is not limited thereto, and the thickness of the surface layer of the substrate can also be other values as long as it is within 0.01 - 6 μm.

[0043] Please refer to Figure 2 , Figure 2 , which is a schematic structural diagram of a coated separator provided by another embodiment of the present invention; wherein Figure 2 The coated separator in the shown embodiment is different from the Figure 1 coated separator in the shown embodiment in that the first crosslinked structure and the second crosslinked structure are both formed on both sides of the substrate. Except for this, other aspects of this embodiment are the same as those of the Figure 1 shown embodiment and will not be described in detail here.

[0044] In addition, the present invention also provides a battery, including: a separator, a positive electrode, a negative electrode, and an electrolyte, and the separator is the Figure 1 or Figure 2 coated separator described above.

[0045] Although the present utility model is disclosed as above, the present utility model is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to the scope defined by the claims.

Claims

1. A coated diaphragm, characterized in that: include: A substrate and a coating formed on one or both sides of the substrate; The coating comprises a first coating portion and a second coating portion; The first coating portion is in contact with the substrate, and the second coating portion is located on a side of the first coating portion away from the substrate; wherein the first coating portion and the surface layer of the substrate form a first cross-linked structure, and the second coating portion is a second cross-linked structure; The first cross-linked structure and the second cross-linked structure are both network structures, and the first cross-linked structure and the second cross-linked structure are integrated cross-linked structures, and the first average pore size of the first cross-linked structure is greater than the second average pore size of the second cross-linked structure.

2. The coated diaphragm according to claim 1, characterized in that The first average pore size is 40-46 nm, and the second average pore size is 39-45 nm.

3. The coated diaphragm according to claim 1, characterized in that The crosslinking degree of the second crosslinking structure is greater than the crosslinking degree of the first crosslinking structure.

4. The coated membrane according to claim 3, characterized in that The gel rate of the second cross-linked structure is 67%-85%, and the gel rate of the first cross-linked structure is 20%-35%.

5. The coated membrane according to claim 1, characterized in that The thickness of the first cross-linked structure is 0.01-6 μm, and the thickness of the second cross-linked structure is 0.5-5 μm.

6. The coated diaphragm according to any one of claims 1 to 5, characterized in that: The material of the substrate is organic material.

7. The coated diaphragm according to any one of claims 1 to 5, characterized in that: The total thickness of the substrate is 5-12 μm.

8. The coated membrane according to claim 7, characterized in that The thickness of the surface layer of the substrate that forms the first cross-linked structure with the first coating portion is 0.01-6 μm.

9. The coated membrane according to claim 8, characterized in that The thickness of the surface layer of the substrate forming the first cross-linked structure with the first coating portion is 0.01-1 μm.

10. A battery, characterized in that: include: A separator, a positive electrode, a negative electrode and an electrolyte, wherein the separator is the coated separator according to any one of claims 1 to 9.

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